1. Field of Invention
The invention relates to a control apparatus for a vehicle having an idle stop function, and more particularly to a control apparatus which is suitably used in a hybrid vehicle having a motor (including a generator function) attached to an automatic transmission.
2. Description of Related Art
Conventionally, there have been suggested many vehicles having a so-called idle stop function, that is, a function of automatically stopping an engine for the purpose of saving fuel, reducing exhaust emission, reducing noise and the like when a vehicle stops during traveling and a predetermined stop condition is satisfied. In particular, in Japanese Unexamined Patent Publication No. 2000-264096, there is proposed a control apparatus at a time of restarting the engine, which prevents a driver from having an uncomfortable feeling due to a shock, a vibration and the like caused by an engagement of a forward clutch, in the case that the driver does not have an intention of starting the vehicle, for example, when a charged amount of the battery is insufficient or when a compressor of an air conditioner is operated due to an increase of a room temperature.
This control apparatus is constructed so as to automatically stop the engine at a time when a predetermined stop condition such as an accelerator off, a brake on or the like is satisfied even in the case that a shift position is at a drive position such as a D range or the like, in the vehicle provided with the automatic transmission having the forward clutch. The control apparatus is also constructed so as to restart the automatically stopped engine when a predetermined restart condition such as an accelerator on or the like is satisfied, and execute the restart in a state where the forward clutch is disengaged.
In the control apparatus at a time of restarting the engine, in the case of detecting the driver""s intention of starting the vehicle such as the accelerator on or the like, even when the engine is rotated on the basis of the requirement of charging the battery or the like, a hydraulic pressure of the automatic transmission is generated and a line pressure is directly supplied to a hydraulic servo of the forward clutch according to a rapid pressure increasing control. The hydraulic pressure of the hydraulic servo thus starts to increase in the disengaged state so that a delay in engagement of the forward clutch is caused. Therefore, there is a possibility that the driver may have an uncomfortable feeling. Further, a changeover valve is opened on the basis of the rapid pressure increase control command and quickly supplies the line pressure to the hydraulic servo for the forward clutch so as to slowly increase the hydraulic pressure to thereby smoothly engaging the forward clutch. However, control of a timing or the like of the changeover valve is complicated and troublesome.
Accordingly, the invention thus provides a control apparatus for a vehicle which executes a feedback control for bringing a hydraulic pressure of a hydraulic servo to a state immediately before a frictional engagement element is engaged when a restart control of an engine is executed and the hydraulic pressure of the hydraulic servo is controlled to a predetermined hydraulic pressure, thereby solving the problems mentioned above.
In accordance with an exemplary aspect of the invention, there is provided a control apparatus for a vehicle which executes an automatic stop control of an engine on the basis of a stop condition, and executes a restart control of the engine on the basis of a start condition, including an engagement element which freely interrupts and establishes power transmission between an output of the engine and a drive wheel, a hydraulic servo which freely operates an engagement state of the engagement element and a control unit which executes a feedback control for bringing a hydraulic pressure of the hydraulic servo into a state immediately before the frictional engagement element is engaged, on the basis of the engagement state of the engagement element wherein the control unit starts the feedback control after the hydraulic pressure of the hydraulic servo is controlled to a predetermined hydraulic pressure when the restart control of the engine is executed.
Therefore, since the control unit starts the feedback control of the hydraulic pressure of the hydraulic servo so that the engagement element is brought into the state immediately before engagement, on the basis of the engagement state of the frictional engagement element, after the hydraulic pressure of the hydraulic servo is controlled to the predetermined hydraulic pressure when the restart control of the engine is executed, it is possible to prevent a delay in the engagement of the engagement element, for example, when the start request from the driver exists, while it is possible to respond to a change in time lapse.